In $Group-13$ $(IIIA)$,$Tl$ (thallium) shows $+1$ oxidation state while other members show $+3$ oxidation state. Why?

Extra pure $N_2$ can be obtained by heating :-

In the electrothermal process,the compound displaced by silica from calcium phosphate is

The most stable trihalide of nitrogen is ..... .

$NH_3 + O_2 \xrightarrow[500 \ K]{Pt} A + H_2O$
$A + O_2 \to B$; $B + H_2O \to C + A$
$A, B$ and $C$ respectively are

Given below are two statements:
Statement $I$: The halogen that makes the longest bond with hydrogen in $HX$ has the smallest covalent radius in its group.
Statement $II$: $A$ group $15$ element's hydride $EH_3$ has the lowest boiling point among corresponding hydrides of other group $15$ elements. The maximum covalency of that element $E$ is $4$.
In the light of the above statements,choose the correct answer from the options given below.